Configuring IP SLAs DNS Operations

This module describes how to configure the IP Service Level Agreements (SLAs) Domain Name System (DNS) operation to measure the difference between the time taken to send a DNS request and receive a reply. This module also demonstrates how the results of the DNS operation can be displayed and analyzed to determine the DNS lookup time which is a critical element for determining the performance of a DNS or web server.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Information About IP SLAs DNS Operations

DNS Operation

The DNS operation measures the difference between the time taken to send a DNS request and receive a reply. DNS is used in the Internet for translating names of network nodes into addresses. The IP SLAs DNS operation queries for an IP address if you specify a host name, or queries for a host name if you specify an IP address.

In the figure below Device B is configured as the source IP SLAs device and a DNS operation is configured with the DNS server as the destination device.

Figure 1. DNS Operation

Connection response time is computed by measuring the difference between the time taken to send a request to the DNS server and the time a reply is received by Device B. The resulting DNS lookup time can help you analyze your DNS performance. Faster DNS lookup times translate to a faster web server access experience.

Configures the scheduling parameters for an individual IP SLAs operation.

Specifies an IP SLAs operation group number and the range of operation numbers for a multioperation scheduler.

Step 4

end

Example:

Device(config)# end

Exits global configuration mode and returns to privileged EXEC mode.

Step 5

showipslagroupschedule

Example:

Device# show ip sla group schedule

(Optional) Displays IP SLAs group schedule details.

Step 6

showipslaconfiguration

Example:

Device# show ip sla configuration

(Optional) Displays IP SLAs configuration details.

Troubleshooting Tips

If the IP Service Level Agreements (SLAs) operation is not running and not generating statistics, add the
verify-data command to the configuration (while configuring in IP SLA configuration mode) to enable data verification. When data verification is enabled, each operation response is checked for corruption. Use the
verify-data command with caution during normal operations because it generates unnecessary overhead.

Use the
debugipslatrace and
debugipslaerror commands to help troubleshoot issues with an IP SLAs operation.

What to Do Next

To add proactive threshold conditions and reactive triggering for generating traps (or for starting another operation) to an IP Service Level Agreements (SLAs) operation, see the “Configuring Proactive Threshold Monitoring” section.

Configuration Examples for IP SLAs DNS Operations

Example Configuring a DNS Operation

The following example shows how to configure a DNS operation from Device B to the DNS server (IP address 172.20.2.132) as shown in the “DNS Operation” figure in the “DNS Operation” section. The operation is scheduled to start immediately. In this example, the target address is a hostname and the DNS operation will query the DNS server for the IP address associated with the hostname host1. No configuration is required at the DNS server.

MIBs

Technical Assistance

Description

Link

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Feature Information for Configuring IP SLAs DNS Operation

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Table 1 Feature Information for the IP SLAs - DNS Operation

Feature Name

Releases

Feature Information

IP SLAs - DNS Operation

12.2(31)SB2

12.2(33)SRB1

12.2(33)SXH

12.3(14)T

Cisco IOS XE Release 2.1

15.0(1)S

Cisco IOS XE 3.1.0SG

The IP SLAs Domain Name System (DNS) Operation feature allows you to measure the difference between the time taken to send a DNS request and receive a reply.

IPSLA 4.0 - IP v6 phase2

15.2(3)T

Cisco IOS XE Release 3.7S

15.1(2)SG

Cisco IOS XE Release 3.4SG

Support was added for operability in IPv6 networks. The following commands are introduced or modified:
dns (IP SLA),
show ip sla configuration,
show ip sla summary.